European leaders on Friday signed the EU's first constitution, a diplomatic triumph they hope will give the union a sharper international profile and speed up decision-making in a club now embracing 25 nations.

The treaty was the result of 28 months of sometimes acrimonious debate between the 25 EU (search) governments and now faces ratification in national parliaments. At least nine EU nations also plan to put it to a referendum, increasing chances that it may not take effect in 2007 as scheduled.

A "no" result in any country would stop the constitution in its tracks.

The EU leaders signed the document at the Campidoglio, a Michaelangelo-designed complex of buildings on Rome's Capitoline Hill, along with the leaders of Romania, Bulgaria, Turkey and Croatia -- four candidates for EU membership.

The event was overshadowed by disagreement over the makeup of the next EU executive that stems from misgivings about a conservative Italian nominee.

On the margins of the signing, the leaders sought to resolve the dispute over Rocco Buttiglione, the incoming EU justice commissioner, who is opposed by a large segment of the 732-member European Parliament (search).

The conservative Catholic and papal confidant raised concerns by saying he believed homosexuality is a sin and that women are better off married and at home.

The constitution foresees simpler voting rules to end decision gridlock in a club that ballooned to 25 members this year and plans to absorb half a dozen more in the years ahead. It includes new powers for the European Parliament and ends national vetoes in 45 new policy areas -- including judicial and police cooperation, education and economic policy -- but not in foreign and defense policy, social security, taxation or cultural matters.

The constitution was signed in the sala degli Orazi e Curiazi, the same spectacular hall in a Renaissance palazzo where in 1957 six nations -- Germany, France, Italy, the Netherlands, Belgium and Luxembourg -- signed the union's founding treaty.

EU leaders signed the constitution in alphabetical order by country, led by Belgian Prime Minister Guy Verhofstadt.

"The seeming madness of our founding fathers has become a splendid reality," Silvio Berlusconi, the Italian premier, said in a speech earlier. "Never in history have we seen an example of nations voluntarily deciding to exercise their sovereign powers jointly in the exclusive interests of their peoples, thus overcoming age-old impulses of rivalry and distrust."

Jan Peter Balkenende, the Dutch leader whose nation holds the EU presidency, said economic and political integration has turned Europe into a realm of peace and cooperation that is the envy of nations worldwide.

"We have seen former dictatorships turn into democracies and witnessed the reunification of Europe," he said.

The EU constitution, which includes a hefty charter of fundamental rights, marks a new chapter in European history giving the continent "greater capacity for making Europe more secure, more prosperous, more just," he said.

The internal turmoil over the makeup of the next EU executive commission cast a shadow over the ceremony.

Buttiglione is not the only candidate to have caused a stir.

Laszlo Kovacs, Hungary's former foreign minister and the incoming energy commissioner, as well as Latvia's Ingrida Udre, the next fiscal affairs commissioner, and Neelie Kroes, the Dutch businesswoman nominated to be competition commissioner, have drawn opposition in the European Parliament.

The leaders were to discuss the succession at the EU head office at a brief meeting after lunch with Portugal's Jose Manuel Barroso, the next European Commission president.

On Wednesday, Barroso, withdrew his incoming team from a vote in the European parliament, asking for more time to make changes.

The constitution that must be ratified in the next two years in all EU states is neither the ambitious document Euro-idealists had hoped for, nor the blueprint for a European superstate Euro-skeptics have warned against.